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FL cobidders are operationally distinct from other frequent losers

Intuition (plain-language)

Not every firm that loses a lot is a cover bidder — most are just uncompetitive. So the screen would be useless if cartel-linked losers looked exactly like ordinary losers. They don't: the cartel-linked ones range across more buyers, concentrate on narrower product lines, and keep showing up beside the same winners. Those are footprints of a role played inside a scheme, not of generic weakness — which is what makes the loser-side signal informative rather than just a ranking of weak firms.

🟡 Inside the FL14 stratum, cobidders look different from other always-losers along four economically meaningful dimensions, with effect sizes (Cohen's d) in the 0.3–1.0 band — large in social-science terms.

  1. Buyer breadth (AN-008). Cobidders bid in 136.5 tenders on average vs 76.7 for non-cobidder FLs (d = +0.67); they cross 24.8 unique winners vs 13.5 (d = +1.00).
  2. Product concentration (AN-009). Cobidder product-portfolio HHI is 0.380 vs 0.288 for non-cobidder FLs (d = +0.39) — more focused product portfolios.
  3. Network proximity (AN-008, AN-009). 1.5% of cobidders have a direct-defendant counterpart vs 0.2% of non-cobidder FLs (d = +0.46). FL-bidder-present markets have winner-side HHI 0.178 vs 0.303 — cobidders show up in the more contestable markets.
  4. Bid-level patterns (AN-010, AN-024). Consistent with credible losing roles, not diagnostic of them.
  5. Survives volume matching (AN-041). Cobidders bid in ~1.8× more tenders, so the obvious worry is that the distinctness is just volume. Matching cobidders to non-cobidder FLs on tenders_count (standardized difference 0.49 → 0.00), the profile distinctness holds or strengthens: product HHI d = +0.47, winner-pair spread −0.56, median gap-to-winner −0.25. The distinctness is not a volume artifact. One honest casualty: the AN-031 bid-dispersion elevation collapses (+0.05, n.s.) and is dropped as a volume artifact.

These differences give the loser-side adjacency target economic content and make it harder to reduce the result to ordinary high- volume losing alone — a worry now directly addressed by the volume-matched audit.

Caveat. The distinctness that survives volume matching is structural (product specialization, winner spread, proximity to the winning bid). The bid-conduct distinctness is narrower: one channel survives (median gap-to-winner), while the bid-dispersion sub-signal (AN-041) and the bid-timing battery (AN-042: all Wilcoxon p ≥ 0.23) are documented nulls — so this is not a multi-channel behavioral signature. The reading stays 🟡 because the dimensions are observational, within-stratum, and single-source (BEC × CADE). The first-time-FL channel (AN-021) and the matched quadrant heterogeneity (AN-032) bound a causal-mechanism reading the finding does not assert, not the structural distinctness. The supporting hypothesis H:cobidder-profile-distinct is Partial (strongly supported) on the structural claim; promotion beyond 🟡 / to Confirmed needs non-BEC replication.

Sources.

  • Own analysis: AN-008 (FL characterization), AN-009 (network HHI + proximity), AN-021 (first-time channel — demoted), AN-024 (unified mechanism quadrants), AN-028 (standardized-diff battery, 7 dimensions × 3 comparisons), AN-031 (bid- level gap-to-winner d = -0.28 — behavioral distinctness beyond participation), AN-032 (matched quadrant heterogeneity audit — honest negative finding), AN-041 (volume-matched profile audit — structural distinctness survives matching on tenders_count; bid-dispersion sub-signal does not), AN-042 (volume-matched timing audit — candidate 2nd bid-conduct channel, null).
  • Cross-refs: H:cobidder-profile-distinct; docs/results.md.
  • Macros: \valBridgeTendCob (136.5), \valBridgeTendFLnc (76.7), \valBridgeUniqWinCob (24.8), \valBridgeHHICob (0.380), \valBridgeHHIFLnc (0.288), \valFLwinnerHHI (0.178), \valNonFLwinnerHHI (0.303), \valFTpsCoef (0.062), \valFTpsP (0.312).
  • Validation: backing scripts scripts/28_pbu_characterization.R, scripts/19_network_heterogeneity_2d.R, scripts/30_first_time_fl_matching.R, scripts/35_unified_mechanism.R.